Topic
Brillouin zone
About: Brillouin zone is a research topic. Over the lifetime, 13849 publications have been published within this topic receiving 383077 citations.
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TL;DR: In this paper, the Brillouin theorem was used to optimise the orbitals in a general multi-structure valence-bond wave function, and the resulting VB SCF method is a powerful generalisation of MC SCF to permit the use of non-orthogonal orbitals.
133 citations
TL;DR: In this paper, the optical emission spectrum of a resonantly excited molybdenum disulfide (MoS2) was studied at liquid helium temperature, and 20 peaks in the energy range spanning up to 1400 cm−1 from the laser line, which are related to multiphonon resonant Raman scattering processes, were observed.
Abstract: Optical emission spectrum of a resonantly (λ = 632.8 nm) excited molybdenum disulfide (MoS2) is studied at liquid helium temperature. More than 20 peaks in the energy range spanning up to 1400 cm−1 from the laser line, which are related to multiphonon resonant Raman scattering processes, are observed. The attribution of the observed lines involving basic lattice vibrational modes of MoS2 and both the longitudinal (LA(M)) and the transverse (TA(M) and/or ZA(M)) acoustic phonons from the vicinity of the high-symmetry M point of the MoS2 Brillouin zone is proposed.
133 citations
TL;DR: In this article, the fine structure of the lowest energy excitonic manifold of two nearly spherical PbSe quantum dots of radius R = 15.3 and 30.6 A was computed using atomistic single-particle wave functions.
Abstract: An exciton evolving from an m-fold degenerate hole level and an n-fold degenerate electron level has a nominal m × n degeneracy, which is often removed by electron−hole interactions. In PbSe quantum dots, the degeneracy of the lowest-energy exciton is m × n = 64 because both the valence-band maximum and the conduction-band minimum originate from the 4-fold degenerate (8-fold including spin) L valleys in the Brillouin zone of bulk PbSe. Using a many-particle configuration-interaction approach based on atomistic single-particle wave functions, we have computed the fine structure of the lowest-energy excitonic manifold of two nearly spherical PbSe quantum dots of radius R = 15.3 and 30.6 A. We identify two main energy splittings, both of which are accessible to experimental probe: (i) The intervalley splitting δ is the energy difference between the two near-edge peaks of the absorption spectrum. We find δ = 80 meV for R = 15.3 A and δ = 18 meV for R = 30.6 A. (ii) The exchange splitting Δx is the energy dif...
132 citations
TL;DR: In this article, the authors theoretically investigated the performance of the photonic crystal superprism, that is, the propagating beam quality, the wavelength sensitivity, and the resolution as a narrow band filter at 1.5μm-wavelength range.
Abstract: We theoretically investigated the performance of the photonic crystal superprism, that is, the propagating beam quality, the wavelength sensitivity, and the resolution as a narrow band filter at 1.5-μm-wavelength range. First, we defined the equi-incident-angle curve in the Brillouin zone. Next, we mapped three parameters that represented the abovementioned performance over the Brillouin zone. As a result, we found a narrow design window that allows a high resolution of 0.4 nm along an equi-incident-angle curve but requires an incident beam width of over 100 μm and a device length of centimeter order. It can be an essential high efficiency filter if the input end of the crystal is optimized and the propagation loss is suppressed.
132 citations
TL;DR: Average properties, such as the effective ir dielectric constant and the effective number of valence electrons per atom are calculated for the two polytypes and compared to GaAs and GaP.
Abstract: The optical properties of cubic and hexagonal GaN thin films, grown by electron-cyclotron resonance microwave plasma-assisted molecular-beam epitaxy on silicon and sapphire substrates, respectively, have been studied at photon energies up to 25 eV with conventional and synchrotron-radiation spectroscopic ellipsometry. The fundamental gaps of the two polytypes are located at different energies, namely at 3.25 and 3.43 eV for cubic and hexagonal GaN. Analysis of the dielectric function of the two phases in the region 4.5--9.5 eV with appropriate models yields the energy location and broadening of the observed critical points. These critical points are assigned to specific points in the zinc-blende and wurtzite Brillouin zones, respectively, making use of the latest published band-structure studies and a comparison is made between the corresponding results for GaN, GaAs, and GaP. Measurements in the temperature range from 80 to 650 K provide the temperature dependence of these parameters. The features observed in the reflectivity spectra of hexagonal GaN are discussed in relation to other works. Kramers-Kronig analysis of the reflectivity between 0 and 33 eV of the hexagonal polytype verifies the existence of a broad feature centered at 14 eV. Finally, average properties, such as the effective ir dielectric constant and the effective number of valence electrons per atom are calculated for the two polytypes and compared to GaAs and GaP.
132 citations